The present invention relates to a plasma torch head, comprising at least one fluid passage, an electrode, a nozzle, a current conductor and a bearing surface on a bearing side, a plasma torch shaft, comprising at least one feed line for a gas, a current supply line, at least one fluid passage, a current conductor and a bearing surface on a bearing side and a plasma torch with at least one feed line for a gas, an electrode, a nozzle and a current supply line, the plasma torch comprising a plasma torch shaft containing at least one first fluid passage, a first current conductor and a first bearing surface on a bearing side, and a plasma torch head containing at least one second fluid passage, a second current conductor and a second bearing surface on a bearing side, the first and second bearing surfaces resting axially relative to one another, the at least one first fluid passage being in fluid connection with the at least one second fluid passage, and the first current conductor being in electric connection with the second current conductor.
Plasma torches are known which consist of a plasma torch shaft and a plasma torch head, which can be joined together by means of a quick change connector. In the plasma torch head there are the parts of the plasma torch which wear quickly in operation and have to be replaced frequently. These are above all the electrode, the nozzle and the cover guard. However, it may also be necessary to change from one plasma torch cutting head to another in the case of varying uses of the plasma process, such as between cutting structural steel and cutting stainless steel. In order to do this quickly, a quick change connector is helpful.
German Document No. G 81 32 660.2 describes a plasma torch consisting of a plasma torch shaft, an attachable connector and a plasma torch head. The plasma torch has a locking pin projecting from the coupling surface and a corresponding hole on the opposing coupling surface, in which the locking pin can be inserted when precisely radially adjusted. The plasma torch shaft and the connector are connected in bayonet fashion by means of a sleeve, which can be displaced on the plasma torch shaft, with guide pins that can be inserted into corresponding axial and radial guide grooves in the connector, by subjecting the sleeve to axial pressure and radial movement. Both in the case of manual operation and in the case of automated systems, it is inconvenient first to introduce the locking pin into the hole and then to connect the other contacts for the delivery and supply lines. In addition, damage cannot be ruled out.
German Document No. DE 695 11 728 T2 describes an alignment means and a method for an arc plasma torch system. The arc plasma torch consists of an arc plasma torch shaft and an arc plasma torch head. An overall positioning guide is used in order to align the arc plasma torch with a seat at the beginning. The seat may be a bevelled edge. The seat has two passages with a receiving end and an upper side which are dimensioned such that alignment pins with a specific diameter are received. The alignment pins also have apertures which can permit a gas or fluid to pass through. The surface diameter is greater than the passage diameter and can thus compensate for minor misalignments. A central passage is similarly dimensioned and can likewise conduct a gas or fluid through. In the case of incorrect positioning, damage can be caused to the alignment pins if a force acts in the axial direction of the arc plasma torch after the central passage has been inserted. If the alignment pins are used simultaneously as a passageway for a gas or fluid, this can lead to leaks. Damage to the alignment pins makes it difficult to position and connect the components of the arc plasma torch later, especially if a slight tolerance is required in the axes of the arc plasma torch head and the seat.
In addition, the insertion of two cylindrical bodies of a plasma torch is known in principle. There is, however, a risk of joining the wrong connections together and/or of damaging them. It is also often necessary for the connection to be highly centered. In such cases, the play between an inner and outer cylinder must be very small. Such an arrangement also makes it difficult to join the parts together.
It is therefore an object of the invention to provide a quickly changeable plasma torch head. According to the invention, a plasma torch head has, on its bearing side, a cylinder wall with an outer surface and an annular surface, nVer similar radial indentations and nVor similar radial projections being provided peripherally on the outer surface, where nVer, nVor is ≧0 and nVer+nVor is ≧5. The quantity n represents combined radial indentations and radial projections such that nVer+nVor=n. If n=5, the sum of two adjacent angles at the center by which the projections and indentations or one projection and one indentation are offset from one another is not ≧180° and the five angles at the center are different in size. If n>5, the sum of two adjacent angles at the center by which the projections and indentations or one projection and one indentation are offset from one another is not ≧180° and the n>5 angles at the center are different in size or at least two of the n>5 angles at the center are equal in size. In each case the sum of the respective angles at the center occurring twice and the adjacent angles at the center on either side thereof is <180°.
It will be appreciated that the current conductor can be implemented in integrated and/or separate form in the fluid passageways within the contemplated cope of the invention.
Normally, there are at least three fluid passageways, namely for supplying gas, such as plasma gas, and the feed and return lines for coolant.
The plasma torch shaft, on its bearing side, has a cylinder wall with an outer surface, nVor similar radial projections and nVer similar radial indentations being provided peripherally on the outer surface, where nVor, nVer is ≧0 and nVor+nVer=n≧5. If n=5, the sum of two adjacent angles at the center by which the projections and indentations or one projection and one indentation are offset from one another is not ≧180° and the five angles at the center are different in size. If n>5, the sum of two adjacent angles at the center by which the projections and indentations or one projection and one indentation are offset from one another is not ≧180° and the n>5 angles at the center are different in size or at least two of the n>5 angles at the center are equal in size. In each case the sum of the respective angles occurring twice at the center and the adjacent angles at the center on either side thereof is <180°.
It will be appreciated that the plasma torch heads and shafts may be plasma cutting or plasma welding heads and shafts, respectively, within the contemplated scope of the invention.
One of the plasma torch shaft and the plasma torch head has, on its bearing side, a first cylinder wall with an outer surface and an annular surface and an external diameter D21a, and the other of the plasma torch shaft and the plasma torch head has, on its bearing side, a second cylinder wall with an inner surface and internal diameter D31a, where D31a is >D21a, and nVor similar radial projections and nVer similar radial indentations being provided peripherally on the inner surface, where nVor, nVer is ≧0 and nVor+nVer=n≧5, and a similar number of corresponding indentations or projections in engagement with them being provided on the outer surface. The projections and indentations are further arranged such that when the plasma torch shaft is connected to the plasma torch head, the projections and indentations first have to be brought into engagement before the first bearing surface and the second bearing surface come to abut each other. If n=5, the sum of two adjacent angles at the center by which the projections and indentations or one projection and one indentation are offset from one another is not ≧180° and the five angles at the center are different in size. If n>5, the sum of two adjacent angles at the center by which the projections and indentations or one projection and one indentation are offset from one another is not ≧180° and the n>5 angles at the center are different in size or at least two of the n>5 angles at the center are equal in size. In each case the sum of the respective angles occurring twice at the center and the adjacent angles at the center on either side thereof is <180°.
The specific number and arrangement of projections and corresponding indentations makes it possible to join the plasma torch head and plasma torch shaft together quickly and easily, without jamming. It is merely necessary for the annular surface to be simply brought to rest against the projections, i.e. to be placed in a joining position, and then to be turned relative to the projections until the joint position is reached, in which, when an axial force is applied, the projections and indentations engage with one another. This is particularly advantageous in situations in which the plasma torches are clamped in and are not visually accessible. The rapid exchange of the plasma torch head can be carried out blindly.
In addition, the invention offers a quick-change connection between the plasma torch head and the plasma torch shaft with protection against twisting, a small tolerance between the axes of the plasma torch head and the plasma torch shaft with a high degree of centralisation.
The fluid passageways both for the gas, and also as plasma and secondary gas, and for the coolant, can also be used for transporting current.
It will be appreciated that the plasma torch can be a plasma cutting or welding torch within the contemplated invention scope.
In the plasma torch head, it can be provided that the sum of two adjacent angles at the center is ≦170°. In this way, an even more stable abutment of the annular surface and projections in the joint position is achieved.
According to one particular embodiment of the invention n=5 and the sum of two adjacent angles at the center is not repeated. According to a further particular embodiment, the plasma torch head contains four fluid passageways. In some embodiments, the at least one fluid passage is advantageously provided with a connector.
The current conductor can also be conveniently provided with a connector in some anticipated embodiments. In addition, it can be provided that indentations are rectangular grooves. It will be further appreciated that the grooves can also be other shapes, such as arcuate, triangular etc.
According to one anticipated embodiment, nVer is ≧5. It will be further appreciated that nVor can be ≧5.
In some embodiments, on the inner surface of the cylinder wall, a peripheral chamfer extending radially outwards can, for example, be provided towards the bearing side before the projections. Such anticipated arrangements allow for easier joining together of parts because a larger diameter is available at the beginning of the joining action.
In some embodiments of the plasma torch, for example, the plasma torch head can have a first cylinder wall and the plasma torch shaft can have a second cylinder wall.